Power converters are electrical devices that either convert electric energy from one form to another (e.g. between AC and DC), or change the voltage, current or frequency of the electric energy, or implement some combination of these. They can also provide impedance matching between a source and a load. Power converters can be classified into different categories, such DC-DC, AC-DC, DC-AC, and AC-AC power converters.
The design of stable and reliable closed-loop control systems for power converters finds use in many applications. Several existing theories, design criteria, and guidelines for the control system are available, varying in terms of complexity and application suitability. For example, one common method used to design a stable closed-loop control system for power converters is based on gain and phase margins criteria with Bode-plot analysis. Another method is based around the technique of root-locus design. While such methods are well developed and widely used, they have the drawbacks: For example, the methods are generalized rule-of-thumb design that do not guarantee achieving optimum performance for a given system. The implementation of the methods in designing high performance closed-loop control systems depends on the designer experience. The methods are sensitive to the theoretical approximations used to obtain the transfer function of the power converter. They are sensitive to the limitations and variations of the hardware used; they are sensitive to component parasitic variations of the power converter which may be caused at least by aging, temperature variations, and manufacturing process variations. The methods require a redesign when the power converter is adjusted or upgraded even slightly. In order to implement advanced control schemes to auto-tune the closed-loop control system transfer function, the methods require measuring the new system transfer function each time. This is complicated and requires more hardware to implement. Most on-line auto tuning methods either require interrupting the closed-loop during the tuning operation or require injecting additional signals. This creates a disturbance to the system output which is not desirable in most applications.